tau - Particle Data Group

Citation: K. Nakamura et al. (Particle Data Group), JP G 37, 075021 (2010) and 2011 partial update for the 2012 edition (URL: http://pdg.lbl.gov)
ξ(e or μ) PARAMETER
(V −A) theory predicts ξ =1.
VALUE EVTS DOCUMENT ID TECN COMMENT
0.985±0.030 OUR FIT
0.981±0.031 OUR AVERAGE
0.986±0.068±0.031 81k HEISTER 01E ALEP 1991–1995 LEP runs
0.929±0.070±0.030 36k ABREU 00L DLPH 1992–1995 runs
0.98 ±0.22 ±0.10 46k ACKERSTAFF 99D OPAL 1990–1995 LEP runs
0.70 ±0.16 54k ACCIARRI 98R L3 1991–1995 LEP runs
1.03 ±0.11 1 ALBRECHT 98 ARG E ee
cm =9.5–10.6 GeV
1.05 ±0.35 ±0.04 2 ABE 97O SLD 1993–1995 SLC runs
1.007±0.040±0.015 55k ALEXANDER 97F CLEO E ee cm =10.6 GeV
•••We do not use the following data for averages, fits, limits, etc. •••
0.94 ±0.21 ±0.07 18k ACCIARRI 96H L3 Repl. by ACCIARRI 98R
0.97 ±0.14 3 ALBRECHT 95C ARG Repl. by ALBRECHT 98
1.18 ±0.15 ±0.16 BUSKULIC 95D ALEP Repl. by HEISTER 01E
0.90 ±0.15 ±0.10 3230 4 ALBRECHT 93G ARG E ee
cm =9.4–10.6 GeV
1 Combined fit to ARGUS tau decay parameter measurements in ALBRECHT 98, AL-
BRECHT 95C, ALBRECHT 93G, and ALBRECHT 94E. ALBRECHT98usetaupair
events of the type τ − τ + → (l − ν l ν τ )(π + π 0 ν τ ), and their charged conjugates.
2 ABE 97O assume η = 0 in their fit. Letting η vary in the fit gives a ξ value of 1.02 ±
0.36 ± 0.05.
3 Combined fit to ARGUS tau decay parameter measurements in ALBRECHT 95C, AL-
BRECHT 93G, and ALBRECHT 94E. ALBRECHT95C uses events of the type τ − τ + →
(l − ν l ν τ )(h + h − h + ν τ ) and their charged conjugates.
4
∣ ∣
ALBRECHT 93G measurement determines ∣ξ for the case ξ(e) =ξ(μ), but the authors
point out that other LEP experiments determine the sign to be positive.
ξ(e) PARAMETER
(V −A) theory predicts ξ =1.
VALUE EVTS DOCUMENT ID TECN COMMENT
0.994±0.040 OUR FIT
1.00 ±0.04 OUR AVERAGE
1.011±0.094±0.038 44k HEISTER 01E ALEP 1991–1995 LEP runs
1.01 ±0.12 ±0.05 17k ABREU 00L DLPH 1992–1995 runs
1.13 ±0.39 ±0.14 25k ACKERSTAFF 99D OPAL 1990–1995 LEP runs
1.11 ±0.20 ±0.08 1 ALBRECHT 98 ARG E ee
cm =9.5–10.6 GeV
1.16 ±0.52 ±0.06 ABE 97O SLD 1993–1995 SLC runs
0.979±0.048±0.016 34k ALEXANDER 97F CLEO E ee cm =10.6 GeV
•••We do not use the following data for averages, fits, limits, etc. •••
1.03 ±0.23 ±0.09 BUSKULIC 95D ALEP Repl. by HEISTER 01E
1 ALBRECHT 98 use tau pair events of the type τ − τ + → (l − νl ν τ )(π + π 0 ν τ ), and
their charged conjugates.
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